SELECT * FROM ( SELECT CASE day_1 WHEN 1 THEN CONCAT(诊断年月,'01') END AS yes FROM tabl UNION SELECT CASE day_2 WHEN 1 THEN CONCAT(诊断年月,'02') END AS yes FROM tabl UNION SELECT CASE day_3 WHEN 1 THEN CONCAT(诊断年月,'03') END AS yes FROM tabl UNION SELECT CASE day_4 WHEN 1 THEN CONCAT(诊断年月,'04') END AS yes FROM tabl) t WHERE t.yes IS NOT NULL;
SELECT
CASE day_1 WHEN 1 THEN CONCAT(诊断年月,'01') END AS yes
FROM tabl
UNION
SELECT
CASE day_2 WHEN 1 THEN CONCAT(诊断年月,'02') END AS yes
FROM tabl
UNION
SELECT
CASE day_3 WHEN 1 THEN CONCAT(诊断年月,'03') END AS yes
FROM tabl
UNION
SELECT
CASE day_4 WHEN 1 THEN CONCAT(诊断年月,'04') END AS yes
FROM tabl) t
WHERE t.yes IS NOT NULL;